Self-induction coils for duplex telephone connections according to the pupin system.



K. H. ULSSON & H. B. M. PLEIJEL. SELF INDUCTION COIL S FOR DUPLEX TELEPHONE CONNECTIONS ACCORDING TO THE PUPIN SYSTEM. APPLICATION FILED Nov. 2, I914.

Patented Jan. 11., 1916.

JUIWQNQ Witmeooea I T W 0. In. @1 1 $3M IMZZW I WUTED STATES PATENT @FFICE.

AXEL HERMAN OLSSON AND HEN N ING BERNHARD MATI-IIAS PLEIJ EL, 0F STOCKHOLM, SWEDEN.

SELF-INDUCTION COILS FOR DUPLEX TELEPHONE CONNECTIONS ACCORDING TO THE PUPIN SYSTEM.

Specification of Letters Patent.

Patented Jan. Ill, M9196.

Application filed November 2, 1914. Serial No. 869,954.

To all whom it may concern:

Be it known that we, AxnL HERMAN OLss0N, engineer, and HENNING BERNHARD MATI-IIAS PLnIJnL, professor, both subjects of the King of Sweden, citizens of Sweden, and residing, respectively, at Bergsgatan 16 and Brunnsgatan 2, Stockholm, in the Kingdom of Sweden, have invented certain new and useful Improvements in Self-Induction Coils for Duplex Telephone Connections According to the Pupin System, of which the following is a specification.

Duplex telephone connections consist of two double lines combined in such a way that not only each double line is used for the messages, but also the wires of the one and the wires of the other double line-the so- .called combination or duplex line-are used for a third message. Such a duplex telephone line is shown diagrammatically in Figure 1 of the annexed drawing. By such a combination, it is possible toaugment the number of double lines by fifty per cent.

According to the Pupin system, the usual double lines A, B and A B are provided with so-called double coils, which consist of two windings arranged on each half of an annular iron core, and each one inserted in the one wire of the double line in such away that the iron core is energized without poles from the currents in the two, line branches A, B or A B when speech waves are sent from the apparatus a or b. It is to be observed, that the currents will run in this case in opposite directions in the two line branches of each double 'line. in A and "B, the currents will flow 1n opposite directions when the apparatus a is used. In the combination or duplex line on the contrary, the currents flow from the apparatus 0 in the same direction in the two line branches A and B. The currents in A and B also flow in the same direction; this direction being opposite to that of the currents in A and B. In this case. the iron cores will be provided with poles at the points where the windings meet each other.- in this way, a leakage field is obtained between these two points, which field has a very detrimental eilect upon the adjacent lines, as the messages upon them will be influenced by the said leakage fields. Where the eilect of said leakage fields is neutralized by inserting metal For instance,

covers or screens, another serious disadvantage occurs; namely that the combination or duplex line is subjected to in-- creased resistance on account of the eddycurrents in the said screens. It has also been proposed to avoid the injurious effects of the leakage fields by applying each winding of the double coils on the whole iron core. Hereby of course the leakage field is prevented from arising; but another inconvenience now insures, in that, in the duplex line, no self-induction will be obtained. Other constructions have also been proposed with a view to avoiding the objections above referred to; but most of them introduce efi'ects which injuriously influence the messages. According to the present invention, the difficulties are overcome by using the said leakage fields for loading-the duplexline.

For loading the double line, the usual double coils are used. A double coil of the one double line is combined with a double coil of the other double line by superposing the one coil upon the other in such a way that the points where the two winding halves meet each other correspond, and further in such a way that the poles, which are set up at said points from the currents in the duplex line, are of different kinds. By these means it results, partly that the leakage field of the one core is absorbed by the other so that disturbing effects of the leakage fields upon the adjacent lines are avoided, and partly that eddy-currents in ad- Fig. 1 shows, as stated, one of the systems already known. Fig. 2 shows a duplex tele phone connection arranged according to the present invention, though the coils are not shown as superposed. Fig. 3 shows diagrammatically the two double coils of the two adjacent double lines. Fig. {l shows diagrammatically the two double coils when a message is transmitted between the two speaking appliances 0 0. Fig. 5 shows die D and (P, D are the two double coils.

When the currents pass through the duplex line-when the apparatus 0 is used as transmitterpoles are set up in the coils so that at C a polarity will be obtained difierent from that at C and at D a polarity different from that at D. Of course, C has a polarity different from D, and C a polarity diiferent from D The two coils are in Fig. 3 shown separate; but they are in practice superposed. so that C corresponds to C and D to D The magnetic lines of force will pass partly from D through E to C, thence to C and through E to D and D, and partly the other way: C, C F D, D, F and C.

- Figs. 4: and 5 show how the poles N and S are set up, when speech is transmitted between the speaking appliances 0 0 or be- We claim v 1. Self-induction coils for loading duplex telephone circuits, consisting oftwo double loading coils inserted one in each of the two double lines in order to load them according to the Pupin system, the duplex circuit being loaded by the leakage fields which are produced by the current in the duplex circuit between the two double coils laid together? '2. Self-'ndligation coil for loading duplex telephone circuits, consisting of two double loading coils inserted one in each of the two double lines in order to load them, the two coils being so laid together that the points of the iron cores opposite one another, where poles will be set up by the current in the duplex circuit, are of opposite polarity.

In testimony whereof we have afiixed our signatures in presence of two witnesses.

AXEL HERMAN OLSSON. HENNING BERNHARD MATHIAS PLEIJEL. Witnesses:

GEs'rA PRIsN, HARRY ALBILM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

